1. Field of the Invention
The invention relates to fastener assemblies, and more particularly, to non-removable structural fastener assemblies for aircraft panels or the like.
2. Description of Pertinent Art
Fasteners are used in a variety of applications, wherein surfaces being connected together impose unique stringent requirements for which the fastener must particularly adapt.
The applications, in which rivets or structural fasteners are used in the construction of aircraft, impose some of the most stringent requirements. In particular, the fasteners must secure different members of the aircraft, but resist losing their clamping power under the forces and vibrations imposed upon them by the harsh environment in which they are used.
In assembling panels to the aircraft structure, alignment problems may occur where the panels are to be affixed to the aircraft body. Over the years, aircraft manufacturers have sought various solutions to this problem, such as line hole drilling the panels and body substructure. Due to the size of the panels and the quantity of the holes, the holes on the panels and substructure still get misaligned and installation of traditional fasteners offer many challenges. Therefore, there is a need of a fastener that will have the ability to align the holes drilled during installation. This will reduce the effort required to install the fasteners in the aircraft panels.
In most aircraft fastening applications, the fasteners are made substantially stronger than the strength of the joint. In most cases the joint fails (e.g. hole elongation, edge tear-out, etc.) while the fastener is still in tact. Therefore, there is a need for a fastener that better complements the strength of the joint and offers considerable weight savings sought by the aircraft industry.
It is important to achieve this goal without compromising the standards established by the aircraft industry. Such standards are set forth by industry recognized professional organizations (e.g. National Aerospace Standard (NAS)) or are established by industry leaders as Boeing Airplane Co. or Lockheed Martin.
It is an object of this invention to provide apparatus for permanently attaching two aircraft panels together.
It is a further object of this invention to carry out the foregoing object using parts of a lesser weight than used in the past resulting in a considerable reduction in weight of the overall aircraft. More specifically, for standard structural fastener applications, this invention uses a thread diameter that is smaller then thread diameters used in equivalent diameter fasteners. For example, a xc2xcxe2x80x3 diameter pin generally uses a xc2xcxe2x80x3 diameter thread; but for this invention a xc2xcxe2x80x3 bolt shall incorporate a 0.216 diameter thread with a modified minor diameter and root radius.
It is also the object of this invention to provide a pin with the capability to align the holes on the aircraft panels with the holes on the aircraft structure. This feature allows easier installation of the fastener as in most cases the holes get misaligned during the fastening installation process.
It is still another object of this invention to provide a method for carrying out the foregoing objects.
These and other objects are preferably accomplished by providing a pin having a head at one end, a threaded shaft portion at the other end. A transition section interconnecting the head and the shaft portion, the thread having special characteristics that is created by using a standard thread with outer major diameter D and a minor inner diameter d to provide a thread in the outer thread major diameter DI and an inner thread minor diameter d1. The distance h between the same being between about 55% to 65% of the distance between the original major diameter D and the original minor diameter d. A nut having a main body portion with a threaded throughbore may be threadably mounted on the threaded shaft portion of the pin, the thread of the nut being adapted to mate with the thread of the pin. [Annular ridges separated by grooves may provide the locking elements.] The aforementioned thus creates a fastener with a normal body diameter and modified smaller diameter thread which incorporates features that allows this combination of pin and nut to meet the structural requirements of established standards.